Process for the hydrogenation of nitro compounds



United States Patent 2 Claims. (Cl. 260580) This application is adivisional application of copending application Ser. No. 267,941, filedMar. 26, 1963 now U.S. Patent No, 3,265,636, issued Aug. 9, 1966.

This invention is directed to improved hydrogenation catalysts and totheir use in the catalytic reduction of nitro compounds.

Hydrogenation catalysts containing platinum or palladium supported oncarbon are well known. Such catalysts have been prepared by impregnatingvarious types of carbon supports with noble metal compounds. The carbonused for such supports has been mainly porous carbon of vegetable oranimal origin. Due to the high porosity of such carbons, some of thenoble metal becomes trapped within the pores and thus does notcontribute to the activity of the catalyst. Another disadvantage is thatsuch porous catalysts become fouled with the products of hydrogenation.In the reduction of a nitro compound to the corresponding amine, severalintermediate reduction products are formed which deposit on the catalystand prevent further reduction from occurring in an efiicient manner. Asa result, large amounts of tars are formed, yields are low and thequality of the final product is poor.

In order to overcome these disadvantages, it has been proposed to usenon-porous oleophilic carbon blacks as supports for the noble metal. Anincrease in hydrogenation rates and improved yields of higher qualityproducts have been noted with non-porous carbon supports for thereduction of aromatic nitrobodies and polynitrotriamines as described inU.S. Patent No. 2,823,235.

It has now been discovered that, if a given quantity of a noble metal isdeposited on a non-porous carbon support and admixed with a porouscarbon, the rate of hydrogenation using this catalyst is about twicethat of a hydrogenation process using the same amount of noble metaldeposited on an all non-porous carbon support for various reductionssuch as: 1) reduction of nitrobodies to hydroxy amines in acid media,(Ex. 4) (2) reduction of aromatic chloro nitrobodies, withoutdechlorination, (3) reductive alkylation of aromatic nitrobodies withketones, (4) reduction of aromatic nitrobodies and (5) reduction ofaromatic dinitro diphenyl ethers.

It is surprising and unexpected that the addition of a porous carbon,which in itself is not as satisfactory as non-porous carbon, wouldproduce such a considerable advantageous effect on the rate ofhydrogenation. This results in a substantial saving in the cost of theexpensive noble metal and provides a more economical hydrogenationprocess.

An added advantage to the catalyst of the present invention is thattechnical grade nitro compounds which normally contain very minoramounts of poisons may be very advantageously reduced therewith to givehigher yields of the corresponding amino compounds.

It is, therefore, an object of this invention to provide an improvedhydrogenation catalyst. It is a further object to significantly andunexpectedly increase the rate of hydrogenation of nitro compounds tothe corresponding amines, hydroxyamines, chloroamines amines.

and alkylated These and other objects will become apparent from thefollowing description and claims.

More specifically, the present invention is directed to a novelhydrogenation catalyst Which comprises a nonpor-ouscarbon support havinga surface area within the range of 20 to 150 sq. meters per gram,admixed with an activated, porous carbon support having a surface areawithin the range of 200 to 1000 sq. meters per gram and platinum -orpalladium or a mixture thereof deposited on the total free surface ofthe combined supports at a loading within the range of 0.05 to 1.0% by,weight of the supports. V I

The present invention is also directed to a process for thehydrogenation of nitro compounds to amines using the catalyst heretoforedefined. This process is also directed to the hydrogenation of nitrocompounds to hydroxy amines, chloroamines and N-alkyl amines.

The metals which may be deposited on the non-porous carbon which islater mixed with porous carbon to prac tice this invention'are platinum,palladium or a combination thereof. The hydrogenation rate may beincreased with promotors or activators. It is known that the presence ofadditional metals, metal oxides, or even non-metallic compounds improvethe performance of a catalyst in a reaction of this type. The termactivation is used to indicate that the catalyst has been improved inperformance by having minor amounts of metals or metal oxides,hydroxides or carbonates combined with the metal catalyst. Activationresults in improved hydrogenation rates and greater catalyst life. I

In the present invention, activation is obtained by utilizing the oxidesor hydroxides of iron, nickel, cobalt, magnesium, aluminum, manganese,chromium, vanadium or tungsten, all of which provide an activatinginfluence. Combinations of activators may be used. Fluorides of boron orsilicon may also be used as activators. Such activator may be addedbefore, during or after precipitation of the novel metal from solutionas a hydroxide or carbonate.

The process of preparing the novel catalyst of this invention involvesfirst suspending the non-porous, highly oleophilic carbon in copper-freewater, as described in U.S. 2,823,235. An activator may be added at thispoint as a water-soluble solution of the activator metal salt; asolution of sodium carbonate or caustic is then added to precipitate theactivator metal base carbonate or hydroxide. A solution of alkali metalbicarbonate or car bonate is added to the aqueous carbon slurry. Asolution of the catalyst metal salt is added; the mass is heated toabout 95 C. and held at this temperature until a test portion, whenfiltered, shows no catalyst metal dissolved in the filtrate. Thisprocedure assures that all the catalyst metal has been precipitated. Themass is then reduced by the addition of aqueous formaldehyde at 95 C. orby the use of hydrogen, hydrazine, alcohol, glycerine and the like. Thecatalyst paste obtained after reduction may be dried.',When usinghydrogen, the unreduced catalyst mass is filtered oif and reduction iscarried out just prior to using thefiltered paste for the hydrogenreduction of nitro compounds, whereby the porous carbon is added intothe reduction mass.

The concentration of the catalyst metal on the nonporous, olephiliccarbon support should be between about 1.0 and 10% by weight of thesupport.

The critical feature of this invention is the addition of a porouscarbon to the non-porous carbon containing the metal catalyst. Thisaddition consists of physical addition and mixing of a high surface,porous carbon with the catalyst paste as prepared above or with thedried catalyst. The porous carbon may be added to the reduction vesseltogether with the non-porous carbon-catalyst paste composition/Thereactor should be equipped with an agitator which thoroughly mixes thecomponents. The mixing, both in the dry state and in situ in the reactordistributes the catalyst metal between the non-porous and the porouscarbon, thereby forming the novel catalyst of the invention. The amountof porous carbon added to the oleophilic carbon catalyst is such as toproduce a catalyst having a loading of about 0.05 to 1% of the catalystmetal based on the total weight of non-porous and porous support.

The use of low concentrations or loadings is desirable for thehydrogenation step, but the higher concentrations are preferred foreaseof catalyst preparation. It is preferred to prepare the catalyst athigh concentrations with subsequent dilutions to lower loadings for thehydrogenation. The amount of porous carbon added will depend on theloading of the catalyst metal desired. Preferably the amount of carbonadded is such-as to produce loadings from 0.05 to 1% of catalyst metalbased on the weight of the total carbon. This concentration has beenvfound to be the effective range. The use of porous carb'on to form theinitial concentrate results in loss of catalyst in the pores and it istherefore advantageous to use non-porous carbon for the concentrate.After dilution of the concentrate with porous carbon, the catalyst metaldistributes itself throughout the total carbon Without clogging up thepores of the porous carbon, thereby leaving available reactive catalystsites.

The catalyst of the present invention is quite versatile. Not only doesit reduce nitro hydrocarbons, nitrohalogenated compounds and nitroethers to the corre-' TABLE 'A.EXAMPLES OF NON-POROUS CARBONS HAV- ING ASURFACE AREA OF 20 TO 150 mF/g.

Surface Trade Name Area, Type mfl/g.

Acetylene, Hiflo 60 Acetylene, black, 50% compressed and less structurethan ordinary acetylene black.

Acetylene, Standard 60 Acetylene black, approx. 100% Heavy. compressed,approx. 14 lbs./cu.

Acetylene, Standard 60 Acetylene black, 50% compressed,

Ordinary. approx. 61bs./ cu. ft. Croflex 77 80 Channel black (easyprocessing). Kosmos M 9-1 Medium processing channel black (heavycompressed). Kosmos T 105 Hard processing channel black I (heavycompressed). Dixie 5 140 Ellelctrliical conductive channel ac Sterling R20 Semi-reinforcing furnace black (combustion). Philblack A 29 Highmodulus furnace black (combustion) Statex B 65 Fine particle furnaceblack (combustion). P33 23 Fine particle furnace black (thermaldecomposition). Rubber Grade velvet 25 Lampblack.

. Lampblack (Type '1). Thermax 19 Medium particle furnace black (thermaldecomposition). Spheron No. 6 120 Medium processing channel black Unted65 SPC.- 100 Super processing furnace black. Monarch 81..-. 120Channel black. Vulcan 3 69 Furnace black.

Porous carbns.The porous carbons which may be added to the non-porouscarbon-catalyst composition have a surface area ranging from about 200to 1000 square meters per gram.

TABLE B.-REPRESENTATIVE EXAMPLES OF OARBONS WITH SURFACE AREA GREATERTHAN 200 mfi/g.

Surface Trade Name Area, Type mfl/g.

Darco G-GO 600 Activated wood charcoal. Nuchar (3-1000 1,000 Do. NucharWA 600 D0. Nuchar B-l00 700 Do. Nuehar C-115 700-950 Do.

D0. Do. Do. Do.

Lampblack Type T 208 Activated lampblack (treated Activated. with air at800 F.). Voltex 281 Conductive channel black. Oarbolac-L 920 Channelblack pigment activated. Carbolac-fL- 850 Do. Carbolaci6 750 Do. SuperCarbovar 400 Do. Mogul 340 Do. Mogul Specla 330 Do. ogul 320 Do. Mogul300 Do. Monarch 71 380 Do. Monarch 74 300 Do.

The following are representative examples of the preparation of thepresent novel catalyst and hydrogenation process for the reduction ofnitro compounds utilizing this catalyst.

Example 1 28 parts of Shawinigan Black compression). are stirred atroom, temperature with 700 parts of copperfree Water containingv 11.5parts of sodiumcarbonate. The mixture is stirred and heated to 99 C. 3.5parts of ohloroplatinic acid (equal to 1.4 parts of platinum) dissolvedin 75 parts of water are added dropwise over a period of 30 minutes,while holding the temperature at 99100 C. The slurry is then held atthis temperature for six (6) hours longer to assure completeprecipitation of platinum values. The mixture. is then cooled to 40,diluted with 300 parts of water and the solid content of theresultantmixture is collected by filtration. The catalyst paste parts)represents a catalyst concentrate having a loading of 5% Pt based on theweight of the carbon black- For use in hydrogenation systems, it ismixed with a porous carbon black as described more fully in Examples IVto X below. This example may be repeated with a loading of 5% platinumon the support withSpheron No. 6, Dixie-5 and United 65 SPC, thesecarbon supports having a surface area of 120, 140 and 100 meters pergram, respectively, to achieve essentially the same results.

Example II 10 parts of sodium chloride are dissolved at room temperaturein 50 parts of water. Agitation is started and 0.84 part of palladiumchloride powder (:0505 part of palladium) are added. The mixture isstirred for 2030 minutes at 2930 C. until the palladium chloride iscompletely dissolved. This technique results in the formation of achloropalladite solution. A solution of 0.14 part of chloroplatinic acid,(equal to 0.056 part of Pt in 5.6 parts of water) is added. The mixtureis stirred for 15 minutes and parts of water, 1.36 parts of ferricchloride hexahydrate [or one part of ferrous chloride ('FeCl -4H O)],5.6 parts of Shawinigan Black, and 30 of 9% Pd, 1% Pt, Fe based on theWeight of the carbon. This example may be varied by substituting thenon-porous carbon blacks, Thermax MT, P-33 FT and Philblack A, saidblacks having a surface area of support of 6.6, 18.1 and 29.0 meters pergram, respectively; the loading on these supports is 5% palladium, 0.5%platinum and 5% Fe The catalyst paste so obtained may be dried and mixedwith a porous carbon to form a catalyst composition containing 0.05 to0.1% of catalyst by Weight of carbon support. Preferably the wetcatalyst paste obtained as described in the above example is added assuch to the reactor vessel with an amount of porous carbon necessary togive a catalyst concentration of 0.05 to 0.1% by weight of the totalcarbon in the system.

Example III A dispersion of 5.6 parts of a carbon black (with a surfacearea less than 150 m. /g.) is prepared and 15 parts of sodiumbicarbonate added. The mixture is stirred at room temperature for 30minutes and then a solution of 0.467 part of PdCl (0.28 part Pd in 20parts of 0.55% HCl (dissolved at 95 C.)) and 2.72 parts of FeCl 6H O (or2 parts of ferrous chloride FeCl -4H O) in 50 parts of Water are added.The mixture is heated to 95 C.; and either held one hour to precipitatethe palladium as hydroxide; or 10 parts of 18.5% formaldehyde solutionare added dropwise while stirring vigorously and held for /2 hour toprecipitate the palladium as reduced metal.

In Examples II and III, the catalysts can be activated by using oxidesor hydroxides of nickel, cobalt, magnesium, aluminum, manganese,chromium, vanadium or tungsten, instead of the oxides or hydroxides ofiron as indicated. Combinations of the fluorides of boron and siliconmay also be used as activators.

The reduction of colloidal noble metals can be done by the addition ofaqueous formaldehyde, or by use of hyrogen or other reducing agents suchas glucose, hydrazine, alcohol, glycerine and the like.

Example IV Nitrobenzene is hydrogenated in a 5-liter creased flaskhaving four vertical creases to act as baifles and equipped with astirrer having a vertical 5.5 inch blade, a circular lower edge and amaximum height of 1.5 inches. The stirrer is operated at 600:25 r.p.m.The flask is provided with a heating jacket, inlet and outlet tubes forhydrogen, a manometer and an inlet for introducing a solution ofnitrobenzene in concentrated sulfuric acid. Into the flask are placed1000 g. of water, 66.2 g. of 96% sulfuric acid, 2 g. of Arquad T-50(Tallow trimethyl ammonium chloride), 2 g. of catalyst paste fromExample I (Which contains 0.02 g. Pt; 0.4 g. Shawinigan Black) and 1.97g. of Carbolac-Z. The catalyst loading amounts to 0.84% Pt by weight oftotal carbon.

TABLE I.A.-DILUTION OF 5% PT ON SHAWINIGAN The reactor is flushed withhydrogen and heated to 90 C. A mixture of 94 g. of nitrobenzene and 38.7g. of 96% sulfuric acid is added to the flask at a rate of 1.6 to 1.8ml./ min. While at the same time adding hydrogen at such a rate that thepressure in the flask remains essentially constant. The temperature ismaintained by external cooling at 92-93 C. and the total pressure at 760mm., the partial pressure of hydrogen being about 200 mm. The sulfuricacid added With the nitrobenzene is equivalent to the basic reductionproducts formed, so that addition of the mixture to the flask producesno change in the overall acidity.

Hydrogen is absorbed at a rate of 1.5 cu. ft. per hour. The nitrobenzeneis added in minutes. The solution then contains 66.7 g. of p-aminophenoland 12.8 g. of aniline, equivalent to yields of 81.7% and 19.3%,respectively.

By following the details of Example IV using a catalyst containing 0.42%Pt by weight of carbon support, hydrogen is absorbed at the rate of 1.51cu. ft. per hour giving a yield of 77.6% of p-aminophenol.

A catalyst prepared according to the'method described in U.S. 2,285,277,containing less than 1% Pt by weight of porous carbon support isinactive in the process of Example IV, if the surface area exceeds 600m. g. (see Table VI for results with 1% Pt on Darco-G60).

Catalysts containing 1% Pt (formaldehyde reduced) prepared according toU.S. 2,285,277 by direct deposition of the catalyst metal onto anon-porous carbon black having a surface area less than 150 m. g. areless active than the catalysts of the invention prepared by thedlStI'i-e bution or addition of porous carbon to non-porous catalystsupport (see Table VII).

Similarly, a catalyst prepared according to U.S. 2,823,235 by dilutionof non-porous carbon support with additional non-porous, low surfacearea carbon is less active than the catalyst of the invention (seeTables II and IV).

The following tables list the results obtained with various porouscarbons added to a catalyst paste, prepared as in Example I, in thehydrogenation of nitrobenzene to produce p-aminophenol.

Table I-A shows the activities produced with the carbon surface areaextended to 1700 m. /liter of reaction solution, using 0.02 g. Pt inhydrogenations of nitrobenzene at C.

Table IB shows the results obtained at 0.5% Pt loading (0.015 g. Pt)using a fixed amount of various porous carbons in hydrogenations at C.

Using 2 g. catalyst paste of Example I, 5% Pt on Shawinigan Black (drybasis) containing 0.02 g. Pt; 0.4 g. Shawinigan Black (24 m surfacearea). Total surface area extended to 1700 111. with substrates listedbelow.

BLACK (EXAMPLE I) WITH VARIOUS POROUS CARBON SUBSTRATES (TYPE B)[Reduction temperature 85 0.; 600 r.p.m. agitator speed] SubstrateReduction Rate p-Aminophenol Min. Name Mfi/g. Wt. g. Final Hz Ml. FeedMole Percent Lb./hr./

Added Percent absorp., per Min. Nmm Yield gal.

Pt Load cu. ft. lhr benzene Darco G-60 600 2. 8 0. 63 1. 70 2. 16 61. 075. 5 0. 71 Nuchar (3-1000 1 1, 000 1. 7 0. 1. 40 1. 67 80. 0 81. 0 0.58 Mogul Special 330 5. 1 0. 37 2. 15 2. 50 53. 0 73. 8 0. 79 M ul 3005. 6 0. 33 2. 20 2. 70 50. 0 76. 6 0. 88 920 1. 82 0. 90 2. 30 2. 70 5076. 0 0. 87 850 1. 97 0. 84 2. 33 2. 70 49 71. 5 0.81 280 6.0 0. 31 1.54 2.00 67 81. 0 0. 69

1 Platinum deposited on Nuchar by method of U.S. Patent No. 2,285,277was inactive.

7 Using 1.5 .g. catalyst paste, Example I, Pt on Shawinigan Blackcontaining 0.015 g. Pt; 0.3 g. Black (18 m? surface. area). Extended to0.5% Pt loading with substrates (2.7 g.) listed below.

8 The water layer (470 parts) has a pH of 8.4 and contains 0.42 g.chloride ion per 100 parts, which represents a 0.5 mole percentdechlorination.

7 TABLE I-B. [Reduction temperature 90 0.; 600 rpm. agitator speed]Substrate Reduction Rate p-Aminophenol Total H Min./ Name Mfi/g. Surf.absorp., Ml. Feed Mole Percent Lb./hr./

Area, cu. ttjhr. per Min. Nitro- Yield gal.

In. benzene Super Carbovar 400 1,088 2.10 2.4 57 63.4 0.63 Carbolac46--- 750 2, 043 1. 65 2.0 67 79.4 0. 68 Monarch 71-"- 380 1, 048 2. 402.8 48 72. 5 0.88

By following the procedure of Example IV, the following nitro compoundsare hydrogenated to p-hydroxyamines:

o-Nitrotoluene to 4-amino-3-methylphenol l-nitronaphthalene to4-aminonaphthol o-Chloronitrobenzene to 4-amino-3-chlorophenolm-Chloronitrobenzene to 4-amino-2-chlorophenol 2-nitrobiphenyl to2-amino-5-hydroxybiphenyl Example V A nickel-clad autoclave, jacketedfor heating or cooling with circulating water and equipped with bafiiesand eificient agitation, is charged with: 2000 parts3,4-dichlorol-nitrobenzene; 100 parts of water; 20 .parts of morpholine;3 parts ofcatalyst paste of Example 1 (equal to 0.03 part of platinum ashydroxide and 0.6 part of Shawinigan Black) and 3 parts of Carbolac-Z.

The quantity of morpholine employedcorresponds to 1% of the weight ofnitro-body; that of the catalyst to 1 part platinum to 66,000 parts ofnitrobody. (Note: 1 part Pt to 200,000 parts nitro is also effective.)

Air in the autoclave and lines is then displaced by pressurizing withnitrogen and releasing the pressure through the vent system. Theautoclave is then pressurized to 500 p.s.i.g. and allowed to standwithout agitation for TABLE II.-3,4-DICHLOROANILINE BATC 100: 10 at 20mm. of Hg to yield a 98.8% pure product 3,4-dichloroaniline, having afreezing point of 711 C.

Substitution in Example V of three parts of low surface area m. /g.)Shawinigan Black for the three parts of Carbolic-2 (850 m. g.) gives amuch slower reduction cycle.

Table II summarizes the results obtained using 0.03 and 0.02 part ofplatinum per 2000 parts of 3,4-diohloronitrobenzene and 20 parts ofmorpholine using 5% Pt 0n Shawinigan Black diluted with (l) ShawiniganBlack to 0.83% Pt loading and with (2), and (3) Carbolac-Z to 0.83% and0.59% Pt.

The extension of concentrated catalyst with Carbolac- 2 results in a 2.3fold increase in the reduction rate with no appreciable increase in themole percent dechlorination, and with a decrease in the percent of HClinsolubles.

With the Shawinigan Black dilution (1), the hydrogen pressure startingat 200 p.s.i.g. and 60 C. temperature had to be increased in the first3045 mins. to 500 p.s.i.g. and 90 C. to maintain the rate of hydrogenabsorption, and it requires (4) four hrs. to effect complete reduction.With the Carbolac2 dilution, the absorption occurred rapidly at 200p.s.i.g. pressure, and only a temp. increase was needed to eifectcompletion in 1.8 hours.

11 HYDROGENATIONS PT, MORPHOLINE (2,000

PARTS 3,4-DICHLORO-l-NITROBENZENE) EFFECT OF DILUTIONS WITH SHAWINIGANBLACK AND CARBOLAC-Z Finished Isolated 3,4-dichlor0aniline ReductionPart Dilution Percent Reduction Pt with P Time,

Loading Minutes 7 Mole Percent Percent F.P., Percent pH Percent Purity 1H01 0. N02 2 Dechlor. insol.

0. 03 Shaw. Black 0.83 249 8. 7 0.45 98.3 0. 52 70. 6 0. 01 0. 03Carbolac-Z- 0.83 109 8. 4 0. 54 Y 98. 9 0. 28 71. 2 0. 03 0.02 Carbo1ac20. 59 180 8. 2 0. 71 98. 7 0. 96 70. 5 0. 03

1 By VPO Analysis. 20 minutes to assure a gas tight system. The nitrogenis then displaced with hydrogen by successive pressurizing to 100p.s.i.g. and venting to zero p.s.i.g. The temperature of the circulatingwater in the jacket is adjusted to 60 C.; the agitator started; and thehydrogen pressure is increased to 200 p.s.i.g. The charge absorbshydrogen rapidly with the evolution of heat. The temperature of thecharge rises to 75 C., with the cooling bath temperature held constantat 60 C. The autoclave is repressurized to 200 p.s.i.g. after each 100lb. drop in pressure. After 100 to 109 minutes no further rapid hydrogenabsorption is noted. The charge is then heated to 95 C., and held at 500p.s.i.g. for 30 minutes longer to assure complete reduction.

The hot reduction mass is then filtered, the filtrate ali 2 By TiClTitration.

The following compounds may also be used as halogen suppressors inExample V in place of morpholine-piperazine, N-methyl and N-ethylmorpholine, and magnesium oxide.

By following the procedure of Example V, the following chloronitrocompounds may be reduced:

lowed to settle at to C., and the layers separated. 754-chloro-3-nitrobenzene sodium sulfonate.

Example VI A steel or nickel-clad pressure reactor, which is jacketedfor heating or cooling with water, and which is equipped with bafliesand an efiicient agitator which rotates at 450 r.p.m., is used for thehydrogen reduction. The reactor is charged to about 20-25% of itscapacity with 700 parts of 3,4-dichloroaniline at 75-85 C., 140 parts ofwater, 10 parts of morpholine, 5 parts of catalyst paste of Example I(equal to 0.05 part of platinum as hydroxide and 1 part of Shawinigan*Black) and 15.7 parts of Carbolac-Z. The autoclave is then pressurizedwith hydrogen to 140 p.s.i.g. and the agitator is started. Thetemperature of the circulating bath is adjusted to 93 12 C. Molten3,4-dichloro-1-nitrobenzene is then injected under pressure in portionsof approximately 59 parts each. As the nitrobody is reduced, a drop inpressure is observed due to consumption of the hydrogen. An externalreservoir limits this pressure drop to about 10 p.s.i. This pressuredrop is also accompanied by a rise in temperature. The .temperature iscontrolled between 90110 during the reaction by circulating the water at90:5 C. through the jacket. After each portion of nitrobody is reduced,the system is repressurized with hydrogen to 140 p.s.i.g. prior toadding another portion of nitrobody. In this man ner, each portion ofnitrobody is completely hydrogenated before adding the next portion. Thetime required to reduce each portion of nitrobody is observed and therate of reduction at 135 p.s.i. (average)parts of3,4-dichlorol-nitrobenzene reduced per minute per part of platinum iscalculated (g. nitro/min./g. Pt)e.g. by dividing the weight of nitrobodyby the product of time required for its hydrogenation by the weight ofplatinum used.

The above hydrogenation process can be operated continuously by removingportions intermittently and recycling the catalyst, or it can be runsemi-continuously, by feeding nitrobody until the autoclave is filled to65-75% capacity.

3,4-dichloroaniline is isolated as described in Example Rates ofreduction obtained with additions of Carbolac-2 to platinum loadingsfrom 0.3 to 0.8% using 0.05 part of Pt/2000 parts of nitrobody arecompared in Table III with 5% Pt on Shawinigan Black undiluted. The rateincreases with increase in Carbolac-Z added.

TABLE III.EFFEC'I OF ADDITION OF CARB OLAO2 Parts Percent Pt ReductionRate Oarbolac-2 Loading part nitro/min./

Added part Pt Example VII Reduction rates from dilutions with Carbolac-Z(850 m. /g.), Mogul A (300 rn. /g.), and Shawinigan Black (60 m. g.)using 0.03 g. Pt at 0.3% Pt loadings are illustrated in Table IV. Theeffect of the large surface area is pronounced.

TABLE IV.DILUTION OF PT ON SHAWINIGAN BLACK (EXAMPLE I) 0.3% PT LOADING;0.03 g.

A 400 ml. Hastelloy pressure tube bomb mounted in a Shaker Machine ischarged with 59 g. of p-nitroaniline, 127 g. of methylethyl ketone, 0.22g. of catalyst paste (equivalent to 0.004 g. Pt, and 0.08 g. of Dixie-5on a dry basis), 0.32 g. of Carbolac2, 3,4 ml. of water and 0.1 ml. ofphosphoric acid are charged into the bomb and the equipment is tested at600-700 p.s.i.g. with nitrogen. The nitrogen pressure is then vented andreplaced with hydrogen by repeated pressurizing at 300 p.s.i.g. followedby venting to zero p.s.i.g. 500 p.s.i.g. hydrogen pressure is thenapplied to system while heating to C. The hydrogenation .is controlledmanually at 400-500 p.s.i.g. H pressure. The initial hydrogen absorptionis rapid, and there are 15-17 100 lb. drops in pressure in about 10-12min. This is accompanied by a rapid rise in temperature from 100-500 C.When this initial temperature kick subsides, heat is applied to maintainthe temperature at 175 i3 C., while holding the hydrogen pressure at400-500 p.s.i.g. until no further absorption occurs. The total time forhydrogenation is four hours.

The bomb is cooled to 30:5 C., opened and the liquid two-layer systemremoved by decantation. The charge is filtered to separate catalyst; thewater layer (33.5 g.) separated; and the methylethyl ketone solution ofthe alkylated diamine is concentrated by distillation to :5 C. at 10 mm.Hg to recover the excess methylethyl ketone. The crude concentrate 93.0g. (calc. yield: 94 g. M.W. 220) is finally vacuum distilled at 115 i5C./l.i0.2 mm. Hg to obtain pure N,N'-di(sec. butyl)- p-phenylenediamine.

The results when 1% Pt on Darco G60 (prepared as described by Henke etal., in U.S. 2,285,277) is scubstituted for the catalyst in Example VIIIare not as satisfactory (see Table VIII). The Darco supported catalystis less active and does not filter as readily.

The use of 1% Pt on only non-porous Shawinigan Black as support,resulted in the exclusive formation of p-phenylene-diamine. None of thedesired alkylated product was formed.

Ketones having the formula RCOR wherein R and R have 1 to 4 carbons andare alike or different may be utilized in the place of methylethylketone of this example. P-nitroaniline remains as the other reactant.

Example IX The procedure described in Example VI is also used for thecontinuous hydrogenation of orthonitrotoluene to produce orthotoluidine.

In this process, orthonitrotoluene is injected in portions of 58 partseach under pressure p.s.i.g. H to an agitated slurry at 450 r.p.m. of750 parts of orthotoluidine, 250 parts of water, 3 parts of catalystpaste containing 4.5% Pd; 0.5% Pt; 5% Fe as hydroxides on ShawiniganBlack (equivalent to 0.03 g. Pd-Pt; 0.6 g. Shawinigan Black) and 9 g. ofCarbolac2 at 100:10 C.

The rate of reduction under these conditions is 800 g.orthonitrotoluene/min./ g. Pd-Pt.

Comparative rates obtained from various additions of porous carbons to acatalyst paste containing 4.5% Pd; 0.5% Pt; 5% Fe on Shawinigan Blackare shown in Table V.

TABLE V.EFFECT OF ADDITION OF OARBOLAC-2 ON Nitrocyclohexane2,4,6-trinitrotoluene Beta-nitronaphthalene p-Nitroanisole.

m-Dinitrobenzene 2,4-'dinitrotoluene 2,6-dinitrotoluene NitrobenzeneZ-nitropropane Example X A pressure autoclave equipped with coolingcoils and an efficient agitator is charged with 1100 parts of n-butylalcohol, 100 parts of 4,4-dinitrodiphenylether, and a catalyst mixtureconsisting of catalyst paste containing 0.011 parts of platinumashydroxide on 0.21 part of Shawinigan Black (prepared as described inExample I), and 2.6 parts of Carbolao-Z.

The mixture, after displacing the air in the system with hydrogen asdescribed in Example V, is hydrogenated at 100-130 C. at 300-500 p.s.i.hydrogen pressure. The hydrogenated product is filtered from thecatalyst, and the clarified filtrate is cooled to obtain crystals ofpure white 4,4-diaminodiphenylether.

The addition of Carbolac-2 to 5% Pt on Shawinigan Black results in aseveral .fold acceleration in rate, while using one-half the quantity ofplatinum, e.g. 1 troy oz. of platinum instead of 2 troy oz. ofplatinum/1000 parts of 4,4'-dinitrodiphenylether.

The novel catalysts of the present invention comprising a mixture of lowsurface area, non-porous carbon and Other dinitrodiphenyl ethers whichmay be reduced in the practice of this invention include:2,4'-dinitro-4-methyldiphenyl ether, 3,4'-dinitrodiphenyl ether,2,2-dinitrodiphenyl ether, 2,3'-dinitrodiphenyl ether, 2,4'-dinitro-3-methyl-S-methoxydiphenyl ether and 4,4-dinitro-2-ethyldiphenyl ether.

The following data set forth comparative performances of the catalystsof the prior art which performances substantiate the unexpectedsignificance of the heretofore described novel catalysts of the presentinvention. The

tables referred to are those tables preceding this data.

Results from direct preparation of 1% Pt loadings on high surface areacarb0ns.Catalysts containing 1% Pt (formaldehyde reduced) prepareddirectly by'the procedure described in US. 2,285,277 on high surfacearea supports (type B carbons) such as Darco G-60, Nuchar C- 1000 andCarbolac-Z are less active than the concentrated catalysts of Example Idiluted with the type B carbons.

1% Pt (CH O reduced) on Carbolac-Z (850 m. g.) 01 on Nuchar C-1000 (1000mF/g'.) is totally inactive, as previously indicated. Results from 1% Pton DarcoG (600 m. g.) are shown in Table VI. This catalyst isconsiderably slower, e.g. less active, than diluted catalysts preparedby redistribution of noble metal values from a low surface area supportto a larger surface area as described in Example 1V (compare Table Iwith Table VI).

TABLE VI.-DAROO G-(SO SUPPORT (SURFACE AREA m ./g.=600) [Catalystprepared from chloroplatinic acid, alkali, and formalin as described inU.S. 2,285,277]

Catalyst Reduction Rate pAminophenol Agitator Red.

Speed, Temp., Percent H Ml. M1n./ r.p.m. C. G. Pt G. C It Absorp., Feed]Mole Percent Lb./hr.'/

Load. cu. ftJhr. Min. Nitro- Yield gal.

benzene high surface area, porous carbon as the support for the noblemetal produce a considerable increase in the rate of hydrogenation ofnitro compounds to amines, hydroxy amines, chloroaminesand alkylatedamines. This several fold unexpected increase results in a direct savingin the 55 amount of expensive platinum and/or palladium metal necessaryto reduce the same amount of nitro compound with known catalysts.

TABLE VII.1%

Results from direct preparation of 1% Pt loadings on low surface areacarbon blacks.1% Pt (reduced metal form) prepared directly ontocarbonblacks (US. 2,285,- 277) with surface areas less than mF/g. (type Acarbon blacks) are less active than the catalysts obtained by thedistribution (or dilution) technique. Results are shown in Table VII(compare with Table I).

PT (REDUCED METAL FORM) ON TYPE A CARBONS SUPPORTS(SURFACE AREA 60-120mF/g.)

[Reduction temperature 85 0., agitator speed 800 r.p.rn.l 7

Table VIII shows the results obtained with 1% Pt on Darco G-60 (preparedas described in US. 2,285,277) compared with those of Example VIII.

14 utilizing a hydrogenation catalyst consisting essentially of anon-porous carbon support having a surface area within the range of 20to 150 square meters per gram, said non- TABLE VIII.REDUCTIVE ALKYLAIIONOF p-NITROANILINE WITH METHYL ETHYL KETONE 0.004 g. PT/59 g. PNA

I Percent PPD Equivalent: By Indophenol formation. Blue color formationwith phenol and caustic soda. PPD =p-phenylenendiamine.

It is thus clear that the herein described and claimed inventionrepresents a novel and unexpected contribution to the art.

The preceding representative examples may be varied within the scope ofthe present total specification disclosure, as understood and practicedby one skilled in the art, to achieve essentially the same results.

As many apparently widely difierent embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that this invention is not limited to the specificembodiments thereof except as defined in the appended claims.

The'embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A process for the hydrogenation of nitro compounds No referencescited.

CHARLES B. PARKE-R, Primary Examiner.

JOSEPH P. BRUST, Examiner.

to their corresponding amines which process comprises 3 V-HIM-33.115831!!!" Examine"-

1. A PROCESS FOR THE HYDROGENATION OF NITRO COMPOUNDS TO THEIRCORRESPONDING AMINES WHIC PROCESS COMPRISES UTILIZING A HYDROGENATIONCATALYST CONSITING ESSENTIALLY OF A NON-POROUS CARBON SUPPORT HAVING ASURFACE AREA WITHIN THE RANGE OF 20 TO 150 SQUARE METERS PER GRAM, SAIDNONPOROUS CARBON SUPPORT BEING ADMIXED WITH AN ACTIVATED, POROUS CARBONSUPPORT HAVING A SURFACE AREA WITHINT THE RANGE OF 200 TO 1000 SQUAREMETERS PER GRAM, A NOBLE METAL SELECTED FROM THE GROUP CONSISTING OFPLATINUM, PALLADIUM AND MIXTURES THEREOF BEING DEPOSITED ON THE TOTALFREE SURFACE OF SAID ADMINXED SUPPORTS AT A LOADING WITHIN THE RANGE OF0.05 TO 1.0% BY WEIGHT OF SID WEIGHT.